As a method of performing digital control on a DC voltage generated by a switching power supply, there are a duty mode and a current mode. The current mode has a good response and easily achieves a multi-phase in which a current is distributed to each phase, as compared to the duty mode.
In the current mode, the inductor current of the switching power supply is compared with the digital compensation value of an output voltage. Therefore, when the accuracy of a DA converter is low, oscillation (limit cycle) occurs in the output of the switching power supply.